The invention pertains to a control mechanism for a welder and, more particularly, to a foot pedal for a welder that controls the output current level of the welder.
Foot pedals are commonly used to control the output current level of a welder during a welding procedure. Typically, an operator depresses the foot pedal to increase the output welding current and releases the foot pedal to decrease the output welding current. The foot pedal provides a convenient way for the operator to control the output welding current while freeing the operator""s hands for directing the welding electrode to a location to be welded. Furthermore, freeing the operator""s hands enables the operator to use one hand to guide the electrode to a weld area and use the other hand to guide a consumable electrode to the weld area while using the foot pedal to control the output welding current. Foot pedals commonly include a start button to activate and deactivate the welder. Some types of welders, such as TIG welders, require the welder to proceed through a start-up sequence to initiate the arc prior to welding. Typically, the operator depresses the foot pedal to cause the start switch to activate thereby activating the pre start-up sequence of the welder. Once the pre start-up sequence is completed, the operator further depresses the pedal to increase the output current through the welding electrode.
Although the use of a foot pedal has simplified and enhanced the welding operation, present foot pedal designs have several disadvantages. For instance, current foot pedal controls combine the arc start switch and the output current control in a manner that makes it difficult for an operator to maintain a minimum welding output current after the start-up sequence has been completed. Typically, the operator depresses the foot pedal past the minimum output current level so as to ensure the start button is engaged and an output current at some low level is generated through the welding electrode after the start-up sequence has been completed. Another disadvantage is that when the operator releases pressure on the pedal to cause the output current to decrease, the operator can inadvertently over release the foot pedal, thereby causing the start button to be deactivated, resulting in the arc being extinguished. It is common practice for the operator to increase and decrease the welding current during a welding operation. During such welding operations, the foot is xe2x80x9crockedxe2x80x9d on the pedal between a minimum and maximum position. During this xe2x80x9crockingxe2x80x9d action, the operator can inadvertently decrease the pedal too much thereby causing the arc to extinguish. This inadvertent extinguishing of the arc can adversely affect the quality of the weld, and increase the difficulty of welding.
The inability for the operator to easily determine and maintain a minimum weld current position using a foot pedal also limits the ability of an operator to initiate various types of weld current shut down sequences.
In view of existing deficiencies of current foot pedal controls for welders, there is a need for a foot pedal control that enables an operator to better control the output current of a welder and/or to prevent inadvertent shut down of the welder during the welding operation.
The present invention pertains to an improved foot pedal control for a welder, and more particularly to a foot control for a TIG welder; however, the invention has broader applications and can be used as a foot and/or hand controller for a variety of welders or other electrical apparatus which require the welder and/or apparatus to be started prior to controlling the current and/or other electrical features of the welder and/or apparatus. The control pedal is designed to control the output current level of a welder in a convenient and efficient manner. The control pedal includes a pedal, a start switch and a current level controller. The pedal is movable between an off position, an intermediate position and an on position. The start switch is adapted to generate a start signal that initiates a start up sequence for the welder. Such start up sequence can include the start-up of an arc for a TIG welder, the start-up of a shielding gas control sequence, the start up of an electrode cooling sequence, the start-up of a consumable electrode feeder, and/or the like. The current level controller is adapted to generate a control signal which is used by the welder to produce an output current through the welding electrode. The control pedal is designed such that the start switch on the control pedal can be shifted from a deactivation position to an activation position prior to the current level controller generating a signal that causes the output current level of the welder to increase above a minimum level. Such an arrangement ensures a starting output current level consistency of the welder, thereby enhancing the performance of the welder. The off position of the pedal is defined as a position wherein the start switch of the control pedal is in the deactivation position. Typically, the deactivation position of the start switch results in the termination of the arc on the electrode of the welder. The intermediate position of the pedal is defined as the position wherein the start switch is shifted from the deactivated position to the activation position. The start switch in the activation position causes a signal to be sent to the welder to initiate the welder start up sequence such as, but not limited to, activating the arc at the welding electrode. The physical position of the pedal in the off position and intermediate position may be the same or different, depending on the particular design of the pedal, the position of the start switch and/or the particular design of the start switch. The intermediate position of the pedal is also defined as the position wherein the current level controller generates a control signal resulting in the output current level of the welder to be maintained at a minimum output current level. The on position of the pedal is defined as a position wherein the start switch is maintained in the activation position, and the output current level produces a control signal resulting in the output current level being maintained at some level above the minimum output current level and up to the maximum output current level of a welder.
In another aspect of the present invention, the control pedal is a foot pedal designed to receive at least a portion of a foot and to be moved by the foot to control the output current level of the welder. In one embodiment, the foot pedal moves by rotating or pivoting about a point and/or sliding along a surface at least during the movement of the pedal between the intermediate position and the on position. In one aspect of this embodiment, the foot pedal is designed to be pivoted about a point. In one specific arrangement, the foot pedal is designed to be depressed downwardly by the heel or ball of the foot to cause the pedal to move between the intermediate position and the on position. In another embodiment, the start switch on the foot pedal is designed and positioned such that the foot pedal does not physically move when shifted between the off position and the intermediate position. In one aspect of this embodiment, the start switch includes a depressable button, contact pad, sliding switch, or the like, located on the top surface of the foot pedal to enable the foot of the operator to activate and deactivate the start switch without having to move the foot pedal. In another embodiment, at least a portion of the foot pedal is moved when the foot pedal is moved between the off position and the intermediate position. In one specific arrangement, the foot pedal is designed so that the operator of the welder moves at least a portion of the foot pedal some distance to cause the start switch to shift between the deactivation position and the activation position.
In still another aspect of the invention, the control pedal includes a pedal that has at least two sections that are mountable such that the two sections move at least partially independently of one another. In one embodiment, one section of the pedal is moveable some distance without causing at least one other section of the pedal to move. In one aspect of this embodiment, the pedal includes a first section and a second section. The first section is adapted to cause the start switch to shift between an activation position and a deactivation position. The second position of the pedal is designed to cause the current level controller to generate a signal that results in the output current level to vary from a minimum current level to a maximum output current level. In one arrangement of this aspect, the first and second sections pivot about substantially the same point. In another arrangement of this aspect, the first and second section of the pedal pivot about a different pivot point. In still another embodiment, the first section is designed to perceive the ball or toe of a foot such that the ball or toe of the foot causes the first section to be depressed downwardly resulting in the start switch shifting from the deactivation position to the activation position. In such a design, the start switch is connected to or positioned under the bottom surface of the first section. Once the first section has been depressed sufficiently to cause the start switch to shift between the deactivation position to the activation position, further depression of the first section by the toe or ball of the foot results in the second section of the foot pedal to be depressed resulting in the pedal moving from the intermediate position to the on position. The movement of the second section of the foot pedal from an on position back to the intermediate position is accomplished by releasing the pressure on the first section and/or having the heel of the foot depress the first section to cause the desired movement of the first section.
In yet another aspect of the present invention, the pedal of the control pedal is a foot pedal which includes a heel section. The heel section is designed to inhibit or prevent the foot of an operator from slipping off the back end of the pedal and/or to maintain the foot of the operator in the proper position on the foot pedal. In one embodiment, the heel section includes an abutment flange, wherein the heel of a shoe or the heel of a foot can rest, thereby preventing the shoe and/or foot from slipping back on the foot pedal. In one aspect of this embodiment, the abutment flange has an arcuate shape to conform to the shape of the heel of a shoe or foot. In another embodiment, the heel section is moveable relative to a portion of the foot pedal to adjust the foot position of an operator on the foot pedal. In one aspect of this embodiment, the heel section is moveable along at least a portion of the end of the foot pedal to adjust the length of the foot pedal.
In still yet another aspect of the present invention, the pedal includes a safety engagement designed to inhibit movement of at least a portion of the pedal from the off position to the intermediate position. The safety engagement reduces or prevents inadvertent activation of the startup button by the operator. In one embodiment, the safety engagement resists the movement of the foot pedal until the operator exerts enough force on the foot pedal to overcome the countering force exerted by the safety engagement. In one specific design of this aspect, the foot pedal includes a first section and a second section, and the safety engagement is adapted to resist movement of the first section of the foot pedal which section is designed to shift the start switch between the activation and deactivation positions. In another aspect of this invention, the safety engagement includes a depressable pen which depresses after sufficient force has been applied to the pedal. In another embodiment, the safety engagement is designed to resist the movement of the pedal from the intermediate position to the off position. In this arrangement, the safety engagement reduces or prevents inadvertent deactivation of the start switch until the operator has fully or substantially removed the force being exerted on the pedal.
In a further aspect of the present invention, the pedal of the control pedal is biased in the off position. Such a biasing arrangement ensures that when the operator removes the force applied to the pedal, the pedal moves to the off position, thereby deactivating the welder.
The principal object of the present invention is to provide a control pedal that controls the output current level of a welder.
Another and/or alternative object of the present invention is to provide a control pedal which initiates a start sequence of the welder prior to causing the welder to increase the output current level above the minimum output current level.
Still another and/or alternative object of the present invention is to provide a control pedal which enables the operator to control the output current level of the welder without inadvertently deactivating the welder.
Yet another and/or alternative object of the present invention is to provide a control pedal which is adapted to be used by the foot of an operator.
Still yet another and/or alternative object of the present invention is to provide a control pedal which is adjustable to accommodate various foot sizes and/or foot positions of the operator on the foot pedal.
A further and/or alternative object of the present invention is to provide a control pedal which allows an operator to xe2x80x9crockxe2x80x9d the pedal to cause the welding current to vary between a maximum and minimum current level without the concern of inadvertently extinguishing the arc.
Still a further and/or alternative object of the present invention is to provide a control pedal which allows an operator to maintain the current level at a minimum current level for a period time without the concern of inadvertently extinguishing the arc to enable an automatic arc shut down sequence.